The online auction and shopping company plans to use the office as an outpost for the online information-sharing website Hunch it recently acquired.

eBay signed a deal to take the space for 10 years for rents in the low $50s per square foot. The company was able to secure about seven months of free rent in the deal and a $45 per square foot contribution from the landlord, Chelsea Green Associates, to help cover the cost of outfitting the space with an office installation.

625 Avenue of the Americas.

The Commercial Observer first reported the lease last month.

According to Ross Eisenberg, a Cushman & Wakefield executive who handles the building’s agency work with a team of other C&W brokers, several other tenants were competing for the space. Mr. Eisenberg noted that much of the interest came from tech companies, a burgeoning sector that has become a dominant taker of office space in the city, especially Midtown South.

“The landlord basically told the tenants, since many of them were start ups, that it would need a very large security deposit,” Mr. Eisenberg said. “But in the end, eBay swooped in knowing that we were close to a deal ready to pay a higher rent than the rest. Plus it’s hard to get better credit than them.”

The building’s second floor, which is also just over 35,000 square feet, is set to come available in the coming months and Mr. Eisenberg said that he and his team are marketing that availability in the $60s per square foot, nearly $10 per square foot higher than the current deal.

“There’s just no vacancy out there in Midtown South right now,” Mr. Eisenberg said.

The Sixth Avenue corridor in the Flatiron District, which is known as the Lady’s Mile because it used to be home to many of the city’s department stores, has attracted a number of recent deals. Last year, Meebo took 22,000 square feet at nearby 641 Avenue of the Americas and Infor took 42,000 square feet there as well. Both are software companies.

Grey Advertising is also said to be in talks to take 70,000 square feet at 620 Avenue of the Americas. Estee Lauder just signed a deal for 66,000 square feet at 28-40 West 23rd Street.